Keratoconus is the most common cause for patients who are not suitable for laser in situ keratomileusis (LASIK) surgery, and currently, the keratoconus is one of the major clinical situations for the failure of LASIK surgery, where it must be taken into consideration whether a patient is prone to suffer keratoconus.
At present, the examination for keratoconus is to mainly measure the patient's corneal biomechanical parameters, as the corneal biomechanical parameters of patients suffering keratoconus are lower than normal levels.
Currently, an ocular response analyzer is the only clinical instrument for in vivo measurement of corneal biomechanical properties. Its measurement method is similar to that of a conventional non-contact tenonometer, where a patient is allowed to place his jaw on a holder of the instrument to fix the head, open his eyes as wide as possible with the to-be-tested eye gazing at a green flashing light in the instrument, a “measurement” button is pressed, then a instrument probe will automatically track and get close to the to-be-tested eye and blow out a surge of gas to flatten the cornea, and a range of parameters are measured. On the day of measurement with the ocular response analyzer, the to-be-tested eye must be kept away from any offensive operation and the use of eye drops, and the to-be-tested patient must be measured in the quiet and relaxed environment situations. Measurement is typically conducted for three times in each examination, but will be conducted for 5 times or even more when there are significant differences of measurement data, and the mean value is calculated.
Thus, it is noted that in measuring the corneal biomechanical properties with the current ocular response analyzer, there is a problem that measurement is affected by many factors, and particularly the patient state has a great influence on the measurement results, leading to a low preoperative examination efficiency for laser surgeries.